The present invention relates to analog-to-digital (A/D) converters of the successive-approximation type. Such converters have been implemented in many forms. Representative examples are illustrated in, e.g., U.S. Pat. Nos. 3,501,625 to Gorbatenko and 3,626,407 to Drangeid et al. Likewise, superconductive devices, including Josephson tunneling-junction devices, have been employed to implement various types of analog-to-digital converters. U.S. Pat. Nos. 3,204,211 to Crittenden et al. and 3,327,303 to Hughes et al. show A/D converters using cryotrons, and U.S. Pat. No. 3,458,735 shows A/D conversion with Josephson devices. Those structures, however, are relatively complex and do not utilize the full potential of such devices.